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How to Change Spark Plugs in a Car

1. Consult your vehicle's manual. Look up where your spark plugs are, how many you have, the correct "gap", and the size socket needed to remove them. Also write down the vehicle's make, model, and year.
2. Visit your local auto part's store. Find (either by looking up in the provided reference book or by asking an employee) the correct spark plugs for your vehicle. You may have multiple options.
3. Find out (from the reference book, the packaging, or the employee) if these spark plugs need to be "gapped". Some modern plugs should not be gapped (but others can have different gaps, depending on use in either 6- or 8-cylinder engines, etc.)
4. Take (if needed) a wire-gauge spark plug gap tool and adjust the distance between the two electrodes. Between the electrodes is where a spark is made. One electrode will be an L-shaped piece of metal at one end of the plug, the other a metal stub centered directly across from it. You want the gap between these two electrodes to be equal to the gap number you wrote down before.
5. Park the vehicle, turn off the engine and open the engine compartment. (WARNING: After running a car long, spark plugs can be hottest part of engine -- can require hours to cool enough, but burnt skin takes 3+ weeks to heal.)
6. Locate (with the help of your manual or a repair manual for your vehicle) the distributor wires. The number of wires will be equal to the number of spark plugs your engine has. Often these wires are red or black, and will be equally divided on opposite sides of the engine.
7. Using masking tape, mark each of these wires so that you can return them to the same place when you are done. (Don't rely on memory: if interrupted, easy to forget, and the car can run rough with crossed plug wires. For 8 cylinders, almost impossible to deduce original plug connections -- must then contact expert or study wiring guides.)
8. Remove each distributor wire and set it out of the way. They will come loose with a little twist and pull and then hang to the side. The spark plugs you are replacing are at the bottom of the holes the wires just came from.
9. Using a spark-plug socket, remove each plug from the engine. Now replace each with a new spark plug. Don't overtighten (usually just 1/16 turn, after finger-tight).
10. Replace the distributor wires on the same plugs they originally came from, and remove the masking tape.
11. Close your engine compartment and start your vehicle.

• Using a sparkplug socket (with internal gasket) instead of a conventional socket will help you to not drop a spark plug when removing or inserting them. (If dropped, the gap often changes, must be re-gapped/cleaned.)
• Examine your old spark plugs when you remove them. They should look slightly burnt at the tip, maybe with some white spotting. If they are bent, black, or broken, you could have a bigger problem and should consult a mechanic.
• Diesel engines do not have spark plugs.
• These basic steps apply to replacing spark plugs in all engine types.

• Make sure when replacing spark plugs that nothing falls into the hole the spark plug is threaded into. Use compressed air to blow away dirt and debris right before you remove an old plug.

• Replacement Spark plugs
• A Socket or Spark plug Socket the same size as your sparkplugs
• A Wire-Gauge Spark plug Gap tool (may be optional)

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Added: Tue Feb 07 2006

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